FIPROtec Combo spot-on solution for cats contains Fipronil & the insect growth regulator S-methoprene. These ingredients not only kill adult fleas, ticks & biting lice but also impedes on the flea life cycle. This results in the prevention of any exposed eggs and/or larvae from developing in your home for up to 6 weeks. Kills adult fleas for up to 4 weeks. Kills ticks for up to 2 weeks. Effective against fleas, ticks & biting lice. Prevents eggs laid by exposed fleas from developing for up to 6 weeks.